Process for preparing a mixture of cyclohexanoneo xim-cyclododecanoneoxim

ABSTRACT

Process for preparing a mixture of cyclohexanoneoximecyclododecanoneoxime containing at the most 70 parts by weight of cyclododecanoneoxime, by oximation of cyclohexanone and cyclododecanone with hydroxylamine sulfate, which comprises carrying out the oximation in two stages, the first stage being effected at a pH of 3-4.5 and 80*-90*C, and the second stage at a pH of 5-6 and a temperature of 90*-110*C.

United States Patent Schultz et a1.

PROCESS FOR PREPARING A MIXTURE OF CYCLOHEXANONEOXIM-CYCLODODECANONEOXIM Inventors: Hans-Joachim Schultz, Chur Grisons;Ernst Iliirllrnann, Bamaus; Albert Gehring, Tamins, all of SwitzerlandAssignee: lnventa A.G. fur Forschung und Patentverwertung, Zurich,Switzerland Filed: Mar. 3, 1971 Appl. No.: 120,757

Foreign Application Priority Data Mar. 13, 1970 Switzerland 3758/70 U.S.Cl. 252/1, 260/566 A Int. Cl ..C07c 131/00, C070 131/02,

C070 131/04 Field of Search 252/1; 260/566 A References Cited UNlTEDSTATES PATENTS 2/1967 Nitsch 260/566 1 Aug. 28, 1973 3,429,920 2/1969Rooij 260/566 3,335,183 8/1967 Rooij 260/566 3,070,627 12/1962 Bostianet a1. 260/566 2,820,825 l/1958 Hillyer et a1 260/566 3,428,625 2/1969Strauss 260/239.3

I FOREIGN PATENTS OR APPLICATIONS 199,776 7/1967 U.S.S.R 260/566 A1,245,944 8/1967 Germany 4,222,623 6/1967 Japan 260/566 A PrimaryExaminer-George F. Lesmes Assistant Examiner-William R. Dixon, .lrvAttorney Cecily L. Frey [57] ABSTRACT 9 Claims, No Drawings PROCESS FORPREPARING A MIXTURE OF CYCLOIIEXANONEO XIM-CYCLODODECANONEOXIM' Thepresent invention relates to the preparation of a mixture ofcyclohexanoneoxime and cyclododecanoneoxime. The novel process consistsof a very careful treatment and thus spellsan economical way ofoximation of cyclohexanone and cyclododecanone in a common operation.The mixture of' the oximes so obtained can be rearranged into thecorresponding lactam mixture by Beckmanns rearrangement and the twolactams may then either be separated or directly polymerized to a 6/12copolyamide.

The practical or technical preparation of cyclododecanoneoxime having amelting point of 134C, as well as that of the dodecalactam obtained byBeckmanns rearrangement, melting point 153C implies the necessity ofusing a solvent or melting point depressant due to the high meltingpoints mentioned. Without the aid of such an agent, it is impossible'tocarry out a continuous technical process for preparingcyclododecanoneoxime and dodeca lactam or at least the process becomesvery expensive due to special requirements.- Assolvents aliphatic andcycloaliphatic hydrocarbons are known, among other solvents (see DAS1.269.615, and Brit. Pat. No. 1.126.495). These substances are usuallyseparated by distillation after use, purified, and returned totheprocess.

Particularly suitable solvents are cyclohexanone and its reactionproduct cyclohexanoneoxime in further processing sometimes alsocaprolactam). Cyclohexanone is a solvent which during oximation ofcyclododecanone is converted into cyclohexanone oxime, which in turnacts as melting point depressant for cyclododecanoneoxime formed fromcyclododecanone, so that upon application of certain ratios of theamounts cyclohexanoneoxime/ cyclododecanoneoxime and with certainconditions of oximation, no deposit of solid cyclododecanoneoxime willoccur. When Beckmanns rearrangement is made to follow the oximation,with the use of anhydrous mineral acids, a mixture of the correspondinglactams will be formed from the mixture of the oximes, the mixture oflactams separating upon neutralization with aqueous alkali solutions asliquid phase at temperatures between 80 and 100C due to the meltingpoint depressant influence of caprolactam on dodecalactam.

It is the object of the present invention to provide an improved processfor the oximation of cyclododecanone which avoids the inconvenience ofthe known art of having to separate the inert solvent used heretoforefrom the reaction product, before returning it into the process, byusing instead a solvent which takes part in the oximation. Otheradvantages will become apparent from the following detailed description.

It is thus the special effect and advantage of the invention that theuse of cyclohexanone as solvent in the oximation of cyclododecanoneresults in the solvent undergoing the same conversion as the substanceto be dissolved and that the new compound formed from the solvent hasagain dissolving or melting point depressant properties. The same istrue for the subsequent reactions when applied, namely Beckmann'srearrangement of the oximes and the neutralization of the conversionproducts. In other words: each of the solvents is at the same time avaluable reaction product, which need not be separated or returned intothe reaction.

Due to the requirement of achieving a substantially quantitativeconversion of the ketones as well as the hydroxylarnine, the technicaloximation of cyclododecanone in the presence of cyclohexanone orcyclohexanoneoxime, respectively, that is to say the cooximation of thetwo ketones usually occurs in two stages. In the first stage, theketones are reacted with an insufficient quantity of hydroxylarnine, inthe second stage onexcess of hydroxylarnine is used for completion ofthe oximation of the mixture of ketones. When it is desired to carry outthe co-oximation at temperatures up to'a maximum of l 10C, the ratio ofcyclohexanoneoxime:cyclododecanoneoxime lies preferably between 40:60and 60:40, (parts by weight). When more than percent by weight ofcyclododecanoneoxime are present, the melting point of the mixture isabove 1 10C. This requires an autoclave and is further disadvantageousbecause of the thermal instability of cyclododecanoneoxime. 30 parts byweight is the lower limit for cyclohexnoneoxime and 70 parts by weightthe upper limit for cyclododecanoneoxime for reasons explained.

It has been found unexpectedly that in the conversion of a mixture ofcyclohexanone and cyclododecanone leading to an oxime mixture containingat the most 70 weight percent cyclododecanoneoxime, only or almost onlycyclohexanoneoxime will be formed when only 50 percent by weight of thetheoretical amount of hydroxylamine are used under conditions whichwould be suited, per se, for the formation of cyclododecanoneoxime,namely a temperature of l00C and a pH of 5.0 5.5. This finding issurprising for the reason that the discontinuous oximation of acorresponding ketone mixture with an excess of hydroxylarnine requires amuch shorter reaction time than the cyclododecanone oximation in theabsence of cyclohexanone or cyclohexanoneoxime. The exclusive oximationof cyclohexanone observed is obviously due to the different molecularsize of the two ketones leading to a highly different reactivity.

Thus, in the above mentioned first oximation stage, the socalledhydroxylarnine -deficiency stage, practically only cyclohexanoneoxime isformed. In this stage of the reaction, the presence of cyclododecanonecan be infact dispensed with. Regardless of the fact whether a mixtureof cyclohexanone/cyclododecanone or cyclohexanone alone is present inthat stage, rapid completion of the oximation will lead in any case tothe formation of cyclohexanoneoxime alone. In the second oximationstage, in which an excess amount of hydroxylamine is used, as mentionedbefore, the oximation of cyclododecanone occurs in the presence ofcyclohexanoneoxime, the rate of the reaction being favorably affected bythat presence.

Essentially the oximation process according to the present inventionconsists in carrying out the oximation of cyclohexanone in a first stagewith hydroxylarnine sulfate, and the oximation of cyclododecanone in asecond stage. The important advantage of this mode of operation consiststherein that part of the oximation process is carried out under milderconditions. This is possible due to the fact that the oximation ofcyclohexanone occurs at comparatively mild conditions, namely attemperatures of -90C at a pH of 3.5-4.5. At 80C, cyclododecanone is aliquid and will not hinder the oximation of cyclohexanone. However, theoximation of cyclododecanone will only occur at temperatures of 90-l 10Cand a pH of 4.5-6 at a sufficiently high speed.

Under the above mentioned conditions of oximation of cyclododecanone,hydroxylamine sulfate is already noticeably instable. However, thestability of the hydroxylamine salt can be markedly improved, that is tosay, the loss in substance occurring under the mentioned conditions, canbe definitely reduced, when a hydroxylamine sulfate is used, which isfree of iron or only contains minute traces thereof. It could not beforeseen or expected that iron ions, e.g., in amounts of l ppm/l wouldcatalyse a 20 percent hydroxylamine sulfate solution at 100C and pHvalues above 4.5 in a noticeable, let alone a high degree.

The negative influence on the stability of 10 percent solutions ofhydroxylamine sulfate caused by traces of iron, dependent on the amountof iron and the pH at a temperature of 100C, can be seen from thefollowing table.

The figures indicate decomposition in percent of hydroxylamine sulfateafter 3 hours.

Fe pH of solution ppm/l 4 5 6 0.3 1.5 3.0 1.7 20.5

From the above figures it becomes apparent that the iron contents of thehydroxylamine sulfate solution has great importance under the conditionsat which oximation of cyclododecanone takes place. At pH 5-6 and areaction time of three hours, l-2 ppm iron cause a considerably higherhydroxylamine sulfate .decomposition than 10-20 times as much iron at pH4. These facts stress the advantage of the process according to theinvention where the one oximation is carried out at,

milder conditions of temperature and pH, since the iron contents oftechnical hydroxylamine sulfate solutions cannot be decreased to below 1ppm/l in 20 percent solutions in practice.

The process for preparing a mixedcyclohexanoneoxime/cyclododecanoneoxime according to the invention canbe carried out discontinuously and continuously as follows: In the firststage cyclohexanone alone is oximated, regardless whether a mixture ofcyclohexanone and cyclododecanone is used or the former only. Thereaction is effected with hydroxylamine-sulfate solution at 80-90C,preferably 85C, and a pH of 3-4.5, preferably 3.5-4, within 15-60minutes, preferably 30 minutes. The hydroxylamine sulfate solution istaken advantageously from the second oximation stage and containstherefore only so much hydroxylamine sulfate that there will be acertain excess of cyclohexanone so that the quantitative conversion ofhydroxylamine will be assured. The cyclohexanoneoxime, in whichremaining cyclohexanone and cyclododecanone are dissolved, is treated inthe second stage of oximation at 90-l 10C, preferably l00-l05C, during 24 hours, preferably 3 hours, at a pH 5-6, preferably 5.5, withhydroxylamine sulfate, an excessive amount of the latter beingpreferred. If only cyclohexanone was used in the first stage,cyclododecanone has to be introduced together with thecyclohexanoneoxime in the second stage. The proportionate amounts ofcyclohexanoneoxime/cyclohexanone and cyclododecanone depends on thedesired ratio of the two oximes in the final product. This may be at theleast 30:70, but is preferably :60

- 60:40. As long as the amount of cyclohexanoneoxime is more than 30percent by weight. any desired ratio can be used, since in that rangethere is no limit as regards the melting points. The amount ofhydroxylamine sulfate in that stage is preferably so chosen that on theone hand the ketone groups present will be completely oximized and, onthe other hand, sufficient hydroxylamine sulfate will remain forcarrying out the oximation in the first stage, when taking intoconsideration the decomposition of the salt which is not entirelyavoidable. From what has been mentioned above it is clear that thehydroxylamine sulfate solution should be as free as possible of ironions; it should, for instance, not contain more than 4 ppm/l, andpreferably not more than i ppm/l.

In the following, the invention will be more fully described in anexample, but it should be understood that this is given by way ofillustration and not of limitation. Many of the reaction conditionsdescribed may be modified within the framework of the disclosure givenabove without departing from the reported results.

EXAMPLE Into a vessel A equipped with a stirrer, 36.5 kgs cyclohexanone,58 kgs cyclododecanone, and 333 kgs of an aqueous hydroxylamine solutioncontaining 10 percent by weight of hydroxylamine sulfate are introducedper hour. The hydroxylamine sulfate solution contains at the most 1ppm/l iron ions. The hydroxylamine may, for instance, be obtained froman NO-hydrogenation and is obtainable commercially. The oximationreaction takes place at a temperature of C, a pH of 3.5-4.0 during atime of 30 minutes. The time of dwell is so chosen that thehydroxylamine sulfate is converted quantitatively, whereas due to theketone excess used and the conditions maintained, only about 93 percentof cyclohexanone are converted into cyclohexanoneoxime. The sulfuricacid formed during the reaction is neutralized by continuous addition ofammonia and the pH is maintained at a constant value thereby.

The reaction product which hourly leaves the reaction vesselcontinuously thus consists of an organic phase containingcyclohexanoneoxime together with unreacted cyclohexanone, as well ascyclododecanone, and a very small quantity of cyclododecanoneoxime, andof an aqueous phase which contains salt, namely dissolved ammoniumsulfate alone, being entirely free from hydroxylamine. The separation ofthe phases is carried out in a separating vessel.

The phase containing cyclohexanoneoxime/cyclohexanone/cyclododecanone iscontinuously transferred to a second vessel B with stirrer, into whichat the same time 317 kgs of a 17.7 weight per cent hydroxylamine sulfatesolution are introduced. The iron ion content of that solution is at themost 1 ppm/ 1. The oximation of the remaining cyclohexanone and of thecyclododecanone is effected at -105C at a pH of 5.5 The sulfuric acidformed is likewise neutralized with ammonia. After an average of 3 hoursdwell, there are no longer any ketones to be found in the organic phaseof only small traces. The reaction product leaving the stirring vesselcontinuously, is separated in a serially connected separator into twoliquid phases at l00-l05C. The organic phase consists ofcyclohexanoneoxime and cyclododecanoneoxime in a weight ratio of 40:60.The aqueous phase, which contains still 10 weight per cent ofhydroxylamine sulfate in addition to ammonium sulfate, serves forcontinuous introduction into the stirring vessel A.

When the oximation is carried out in both stages with a hydroxylaminesulfate solution containing 6 ppm/l of iron ions, all other conditionsbeing equal, 420 kgs of hydroxylamine sulfate solution of the sameconcentration are required for the quantitative conversion of theketones. In other words, about percent more bydroxylamine sulfate isconsumed due to the decomposition of the salt caused by the higher ironcontent.

While the invention has been illustrated in a single example, it willbe. obvious to the expert that changes in the details will not interferewith the spirit of the invention as set forth in the appended claims.

What we claim is:

1. Process of forming a mixture of cyclohexanone oxime andcyclododecanone oxime containing a maximum of about 70 percent by weightof cyclododecanone which comprises, in a first stage, contactingcyclohexanone with an amount of hydroxylamine sulphate insufficient toeffect oximation of all the cyclohexanone present, at a temperaturebetween about 80 and about 90 C. and a pH between about 3 and about 4.5,and in a second stage, incorporating in the oximation solution an amountof cyclododecanone sufficient to produce the aforementioned percentageof cyclododecanone oxime, and in the presence of an excess ofhydroxylamine sulphate over that required for the oximation of thecyclododecanone, forming cyclododecanone oxime at a temperature betweenabout and about C. at a pH between about 5 and about 6, whereby thecyclohexanone oxime formed in the first stage acts to maintain thecyclododecanone oxime in solution.

2. The process according to claim 1, wherein the first stage is carriedout for 15-60 minutes and the second stage for 2-4 hours.

3. The process according to claim 2, wherein the first stage is carriedout for 30 minutes and the second stage for 3 hours.

4. The process according to claim 1, wherein the first stage is carriedout at a pH of 3.5-4 and a temperature of 85C.

5. The process according to claim 1, wherein the second stage is carriedout at a pH of 5.5 and a temperature of l0O-105C.

6. The process according to claim 1, wherein the hydroxylaminesulfatesolution does not contain more than 4 ppm/l iron ions.

7. The process according to claim 1, wherein the hydroxylamine sulfatesolution does not contain more than 1 ppm/l iron ions.

8. The process according to claim 1, wherein the remaining hydroxylaminesolution is re-used in the first stage for oximation.

9. The process according to claim 1, wherein the cyclododecanone isintroduced and is present in the first stage.

1 UNITED STATES PATENT OFFICE CERTIFICATE OF- CORRECTION Patent NO.307550 Dated A118- 973 Hans-Joachim Schultz) et a1 Inventor-(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Below the line United States Patent [191 "Schultz et a1" should read.Sohultze et al--:

In the first line 01*[75] Inventors:

"Schultz" should read --Schultze In the second vline of that paragraph,change "Barnaus" to Domat-Ems gfiri n Signed and sealed this lL th dayoi May 19714.

(SEAL) Attest: I

EDWARD IhFLEI'CHERQJR. I C. MARSHALL DANN Attesting Officer Commissionerof Patents F po'wso v uscoMM-oc OOS IG-PBO ".5, GOVERNMENT PRINTINGQIIICE 2 1". J.-3J4

UNITED STATES PATENT OFFICE CERTIFICATE OF- CORRECTION Parent No. 35755, Dated M18028 9 973 Inventor-(s) Hans-Joachim z) at 8.1

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Below the line United States Patent [193 "Schultz eta1" should readSohultze et a1 In the first line of 75] Inventors;

"Schultz" should read .--Schu1tze In the second: .line of thatparagraph, change Barnaus to Domat-Emsij riscns a I Signed a d sealedrhis 1Lp;1;1hay I of May 19m.

(SEAL) Attest: EDWARD 1-I.FLE1J0HER,JR. c. MARSHALL DANN AttestingOfficer" I i 1 Commissioner of Patents I 1 FORM Po-wso (10-69)- Y 7uscoMM-Dc wan-m v u.s. aovumanv rmn'rma qmct "II o-su-ou

2. The process according to claim 1, wherein the first stage is carriedout for 15-60 minutes and the second stage for 2-4 hours.
 3. The processaccording to claim 2, wherein the first stage is carried out for 30minutes and the second stage for 3 hours.
 4. The process according toclaim 1, wherein the first stage is carried out at a pH of 3.5-4 and atemperature of 85*C.
 5. The process according to claim 1, wherein thesecond stage is carried out at a pH of 5.5 and a temperature of100*-105*C.
 6. The process according to claim 1, wherein thehydroxylaminesulfate solution does not contain more than 4 ppm/1 ironions.
 7. The process according to claim 1, wherein the hydroxylaminesulfate solution does not contain more than 1 ppm/1 iron ions.
 8. Theprocess according to claim 1, wherein the remaining hydroxylaminesolution is re-used in the first stage for oximation.
 9. The processaccording to claim 1, wherein the cyclododecanone is introduced and ispresent in the first stage.